The invention concerns an electromagnetic drive mechanism for the pin in a matrix printing head that has a magnet with an articulated armature, whereby the free end of the armature acts on the pin and can be returned to its disengaged position by a recovery mechanism.
German as 1 817 848 discloses a printing-pin magnet with electromagnetic attraction and repulsion. This device, however, requires two complete separate magnet systems, each with its own armature.
The combined mass of the two armatures decelerates operation. Also necessary is a spring to establish the armature's disengaged position, and the spring must also be activated during attraction, using up additional energy during the period and decelerating the attraction.
A system of articulated-armature magnets for a line printer with an electromagnetic recuperating magnet is known from German GM 1 923 036. Its armature is in the form of a bent lever, one arm of which has a hammer mounted on it and the other arm of which constitutes the actual armature. The end of the armature is wider, and the pole surfaces of the magnets, which are positioned on each side, are at an angle to each other, which makes the mechanism complicated to assemble. Since the armature is several times larger than any of its magnetically active regions, it operates much more slowly than a simple magnet.
German 3 139 502 C2 discloses a rapid-excitation circuit for printing magnet along with circuitry for intercepting the turn-off current with a buffer capacitor, whereby the temporarily stored capacitor charge flows later, once the magnet has been completely drained of current, through the same coil in the opposite direction, resulting in combination with a permanent magnet in the armature circuit in a recovery action. This design depends in its function on many components and their tolerances.
A matrix printing head with an armature that is turned and milled from a ferromagnetic blank is known from German 2 201 049 B2. Although the ends of the armature are in the same plane, they can be aligned in that plane only by turning and not by lapping because of the presence of an elevated edge with a groove for securing the armature that does not allow further processing. Since the armature rests against the yoke in the center, the width of the interferric gap is dictated by the distance between a cover-support surface and the face of the armature, by the thickness of the stop, and by the thickness of the armature, and accordingly depends on, among other factors, the mutual tolerance to which the face and the supporting surface can be turned.
The object of the invention is a simple and relatively small articulated-armature magnet system for a matrix printing head that will operate rapidly.